Prevalence of Anti-SARS-CoV-2 Antibodies in Poznań, Poland, after the First Wave of the COVID-19 Pandemic

Abstract

In comparison to other European countries, during the first months of the COVID-19 pandemic, Poland reported a relatively low number of confirmed cases of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. To estimate the scale of the pandemic in Poland, a serosurvey of antibodies against SARS-CoV-2 was performed after the first wave of COVID-19 in Europe (March–May 2020). Within this study, we collected samples from 28 July to 24 September 2020 and, based on the ELISA results, we found that 1.67% (25/1500, 95% CI 1.13–2.45) of the Poznan (Poland) metropolitan area’s population had antibodies against SARS-CoV-2 after the first wave of COVID-19. However, the presence of anti-SARS-CoV-2 IgG antibodies was confirmed with immunoblotting in 56% (14/25) samples, which finally resulted in a decrease in seroprevalence, i.e., 0.93% (14/1500, 95% CI 0.56–1.56). The positive anti-SARS-CoV-2 IgG results were associated with age, occupation involving constant contact with people, travelling abroad, non-compliance with epidemiological recommendations and direct contact with the novel coronavirus. Our findings confirm the low SARS-CoV-2 incidence in Poland and imply that the population had little herd immunity heading into the second and third wave of the pandemic, and therefore, that herd immunity contributed little to preventing the high numbers of SARS-CoV-2 infections and COVID-19-related deaths in Poland during these subsequent waves.

RETRACTED: The Safety of COVID-19 Vaccinations—We Should Rethink the Policy

“…An innate immune reaction is difficult to gauge. Thus, low seroprevalence figures [ 20 , 21 , 22 ] may not only reflect a lack of herd immunity, but also a mix of undetected cross-reactivity of antibodies to other coronaviruses, as well as clearing of infection by innate immunity.…”

Impact of Two Different Recruitment Procedures (Random vs. Volunteer Selection) on the Results of Seroepidemiological Study (SARS-CoV-2)

“…The method of recruiting volunteer participants in our study was similar to the methods used in other population-based studies [ 9 ]. In our study, we employed a variety of means in order to reach the population, ranging from traditional press, through television, and ending with the internet.…”

“…The Italian cohort showed a seroprevalence of 14.4% in a period from March to June 2020 [ 8 ]. During the first months of the COVID-19 pandemic, Poland reported a lower incidence of confirmed cases compared to other European countries [ 9 ]. The seroprevalence in the population of Poznan metropolitan area in Poland was 1.67% (sample collection between the end of July and the end of September 2020), finally dropping to 0.93% after immunoblotting verification [ 9 ].…”

SARS-CoV-2 Infection Prevalence in the Population of South-Eastern Poland

“…Moreover, materials were collected in the area of Lublin, which also contributes to a higher number of reported cases among Lublin residents. The reduced number of SARS-CoV-2 infections in smaller towns and villages may be due to poorer access to the health care system and diagnostic centers [11]. In Poland, during the partial freezing of the economy, the number of extra-family contacts was significantly reduced, and at the end of April 2020, the number of people contacted by a person infected with COVID-19 was almost three people.…”

“…22,23]. The real-time PCR method is widely in the diagnosis of SARS-CoV-2 due to its high sensitivity, specificity, and the ability to test numerous samples at the same time [11,24]. Our study used an automated RNA-isolation method that reduces errors caused by the "human factor".…”